Various types of disconnect or uncoupling devices to separate a load lowered on the end of a cable are known in the art. Certain types of devices constitute "explosive bolts" arranged to be detonated and thereby break a connection between the load and the end of a cable or other structure when it is desired to separate the same. In other instances, electrical devices such as electrically operated locking and unlocking structures which can be controlled from the upper end of a cable are provided to separate or drop a load from the end of a cable. Another class of such devices, purely mechanical in nature, is automatically responsive to engagement of a load with the ground to separate the load from the cable used in lowering the load. Generally these latter type disconnect devices release the load in response to removal of the weight on the device as when the load engages the ground.
Wholly mechanical type devices have certain advantages over chemical or electrically operated devices. First, they are normally less expensive. Second, they can normally be reused. On the other hand, where the connecting device is releasable in response to removal of the weight of the load, inadvertent separation could occur. For example, the weight of the load might be relieved as a consequence of some action other than the load actually engaging the ground, such as a sudden drop in the aircraft supporting the upper end of a cable as a consequence of an air pocket. The resulting momentary relief of tension in the cable on the connecting device could result in inadvertent disconnection while the aircraft and load are still at a high altitude so that the load simply falls to the ground and smashes.